good or bad idea ?

i have a massive 16 inch patton fan the ones that sound like planes taking off. i already tried putting one of my more modest fans point directly onto the motherboard ( i removed one side of the case ) and the temps dropped a decent amount and i was wondering espicially if it would be a bad idea to put my big fan like right next to the mobo im not concerned about noise im more concerned about debris and dust ? do i need to be worried about dust and other stuff ??

That's overkill. You could get the same effect with a few cleverly placed regular 12V fans. Like one right over the CPU ducted right into the HSF. Hell, you could even have a passive duct and it would do alot of good. Then a second right over the AGP/northbridge tends to help.

The fan you're thinking of using would probably do more bad than good, especially with that much power in it. It'd distort the mobo with the wind, blow crap in there, and you say you don't care about noise but just put in on the floor next to you and surf the web for a few hours and see how your ears feel.

--Illah